AbstractIn the present investigation the systematics, on the basis of external, morphological characters, of 27 different species of catfishes of the Punjab, Pakistan, belonging to 17 genera and 6 families, has been given. The food and feeding habits of 22 different species of catfishes of the Punjab, Pakistan, was determined on the basis of stomach content analyses. Diurnal pattern of feeding and seasonal variations in food and feeding habits of seven catfishes was also studied. It was found that catfishes of the Punjab belong to piscivores and carnivores. They mainly feed at the time of twilight and in the months of February to April and September to November and fast during the breeding season and winter.

On the basis of the study of the gastrointestinal tract of Aorichthys aor sarwari, in detail and comparing it with Wallago attu and the rest 14 catfishes it was found that there are considerable differences in the anatomy and morphology of the alimentary tracts of catfish species that feed upon different prey types. The overall morphology and anatomy of the alimentary tract appears to be, to a cumsiderable extent, 'hard-wired' to the normal diet of the catfish. Definite correlation exists between the shape of mouth, lips, form of teeth and gill rakers, the nature of diet and feeding habits. The size and external shape of the stomach differs among species due to their feeding habits; so does the relative length of the intestine. Phylogeny also affects the type of the structure of these organs and also on the extramural organs of the catfishes. Pancreas compactum is present in the family Siluridae only.

Histology of the gastrointestinal tract of Aorichthys aor Sarwari was studied in detail and of Wallago attu in short. Mouth, having similar structure, possesses taste buds for gustation, mucous cells for lubrication and protection and club cells producing alarm substance for fright reaction. The oesophagus has characteristic mucosal folds; taste buds very few, restricted only to anterior portion, and abundant mucous cells are present. The gastric mucosa consists of the columnar cells of the surface epithelium and glandular cells. The former are identifiable by their location and by the shape and distribution of granules which contain neutral and. acid mucosubstances. The simple tubular glands are located y in the corpus ventriculi and gastric caecum and are formed by single type glandular cells. The mucosa of the intestine is lined by a simple columnar it helium which possesses the brush border of microvilli (apical plate) typical absorptive tissue. Mucus-secreting goblet cells occur scattered among the epithelial cells and show a positive periodic acid-Schiff (PAS +) reaction. Mucosa of the rectum is typically richly endowed with goblet cells. The liver is complicated structure consisting of anastomosing epithelial lamellae separating b1ood sinusoids. Exocrine pancreatic tissue surrounds all of the portal veins and an anastomosing bilaminar meshwork of hepatocytes. The wall of the gall adder consists of columnar epithelium, a thin submucosa and a muscularis of smooth muscle cells. The diffused exocrine pancreas consists of ramified tubules acini within the liver except in Siluridae where pancreas compactum is present. The secretory cells form acini with narrow lumina, and a common pancreatic duct opens to the anterior intestine.

Digestive system of the catfishes of the Punjab, Pakistan are of the carnivore type, with characters of both primitive as well as advanced ones. The narrow, medium and wide, non-protractile mouth, lack of gastric caecum in A aor sarwari, cardiform and villiform teeth; relative gut length ratio of near. Unity, diffused pancreas, one type of secretory cells in the gastric glands are all primitive characters whereas the conical maxillaries and molariform vomerine and mandibular teeth in Rita rita, stomach with well developed gastric caecum, pancreas compactum in the family Siluridae, gill rakers of the biserial dimorphic monacanth type are advanced characters.